This application relates to a refrigerant system utilizing tandem compressors sharing a common condenser, but having separate evaporators, and incorporating air reheat means by using refrigerant circulating throughout the system.
Refrigerant systems are utilized in applications to change the temperature and humidity or otherwise condition the environment. In a standard refrigerant system, a compressor delivers a compressed refrigerant to a condenser. From the condenser, the refrigerant passes through an expansion device, and then to an evaporator. As air is blown over the evaporator, moisture is removed from the air and its temperature is reduced. From the evaporator, the refrigerant returns to the compressor. Of course, basic refrigerant cycles are utilized in combination with many configuration variations and optional features. However, the above provides a brief understanding of the fundamental concept.
In more advanced refrigerant cycles, a capacity of the refrigerant system can be controlled by the implementation of so-called tandem compressors. The tandem compressors are normally connected together via common suction and common discharge manifolds. From a single common evaporator, the refrigerant is returned through a common suction manifold to each of the tandem compressors. From the individual compressors the refrigerant is delivered into a common discharge manifold and then into a common single condenser. The tandem compressors are also separately controlled and can be started and shut off independently of each other such that one or both compressors may be operated at a time. By controlling which and how many compressors are running, control over the capacity of the entire system is achieved. Often, the two compressors are selected to have different sizes, such that even greater flexibility in capacity control is provided. Also, tandem compressors may have shutoff valves to isolate some of the compressors from the active refrigerant circuit, when they are shutdown. Moreover, to improve compressor lubrication, pressure equalization and oil equalization lines are frequently employed.
One advantage of the tandem compressor system is that more capacity control is provided, without the requirement of having each of the compressors operating on a dedicated circuit. This reduces the overall system cost.
However, certain applications require cooling at various temperature levels. For example, low temperature (refrigeration) cooling can be provided to a refrigeration case by one of the evaporators connected to one compressor and intermediate temperature (perishable) cooling can be supplied by another evaporator connected to another compressor. In another example, a computer room and a conventional room would also require cooling loads provided at different temperature levels, which can be achieved by the proposed multi-temp system as desired. However, the cooling at different levels will not work with application of a conventional tandem compressor configuration, because a separate evaporator for each cooling level would be required. Thus, non-tandem independent compressors must be used in a dedicated circuit for each cooling level. Furthermore, each circuit must be equipped with a dedicated compressor, dedicated evaporator, dedicated condenser, dedicated expansion device, and dedicated evaporator and condenser fans. This arrangement having a dedicated circuitry for each temperature level would be extremely expensive.
In some cases, while the system is operating in a cooling mode, the temperature level at which the air is delivered to provide comfort environment in a conditioned space may need to be higher than the temperature that would provide the ideal humidity level. Generally, the lower the temperature of the evaporator coil more moisture can be removed from the air stream. These opposite trends have presented challenges to refrigerant system designers. One way to address such challenges is to utilize various schematics incorporating reheat coils. In many cases, a reheat coil placed in the way of an indoor air stream behind the evaporator is employed for the purposes of reheating the air supplied to the conditioned space after it has been cooled in the evaporator, where the moisture has been removed as well.
While reheat coils have been incorporated into air conditioning systems, they have not been utilized in an air conditioning system having an ability to operate at multiple temperature levels.
This invention offers a solution to this problem where tandem compressors can be used for operating a refrigerant system at multiple distinct temperature levels, and with the system control and operation flexibility provided by a reheat coil.